In collaboration with Dr. B. Herzlich, we studied 384 patients undergoing coronary arteriography for a variety of clinical indications, including ejection fractions, which were calculated in patients undergoing ventriculograms. Our study showed that Vitamin B12 deficiency (< 300 pg/ml) and plasma homocyst(e)ine (> 16 nmol/ml) was associated with a low left ventricular ejection fraction, and that plasma homocyst(e)ine is inversely correlated with serum Vitamin B12, folate and left ventricular ejection fraction, and directly correlated with creatinine and age. There was no apparent correlation between plasma homocyst(e)ine and extent of coronary artery disease. This data demonstrates that Vitamin B12-deficient patients may have significantly lower left ventricular ejection fractions. Whether low left ventricular ejection fraction results in malabsorption of Vitamin B12 and/or Vitamin B12 deficiency warrants further investigation.